It is known in the prior art to effect ignition in internal combustion engines by means of high- and low-tension magnetos or conventional battery ignition systems. Such ignition equipment employs contacts which conduct heavy current and, therefore, lacks operating reliability and needs much attention in service.
To eliminate these disadvantages, solid-state ignition systems have been devised which generate the necessary spark-producing energy, distribute it between the ignition coils of the appropriate cylinders and time the ignition without the use of such contacts.
As an example, reference can be made to the ignition system diagrammatized in the American magazine "Diesel and Gas Turbine Progress," 1968, No. 4, page 4.
This prior art ignition system comprises a power source in the form of an alternator having two separate output windings. One of these windings is connected to a capacitor through a full-wave rectifier in series with a voltage stabilizer. Connected to the capacitor upper plate is the anode of a thyristor whose cathode is connected to the primary winding of the ignition coil.
Pulse shaping is effected by provision of a pulse transformer whose secondary winding is connected to the junction between the thyristor control gate and cathode. One end of the primary winding is connected to a capacitor charged through a voltage divider, the other end of the primary winding is connected to the anode of the control thyristor whose gate is connected to the winding of a control pulse generator.
The quantity of thyristors and pulse shapers corresponds with the number of the cylinders in the engine. While one of the thyristors is operating, the others are standing by. Under these conditions voltage may be induced in the pulse shaper system, causing inadvertant operation of the thyristors. To prevent the thyristors from inadvertant operation, a negative bias supplied from the other winding of the alternator is fed to the thyristor gates.
This prior art ignition system suffers from the disadvantage that it has to employ a complicated arrangement for supplying a negative bias to the thyristor gates and that the sensitivity of the pulse forming system is adversely affected.